Up to now, the diaphragm has been clamped to the valve seat such that the drive housing, for example, is fastened to the valve body by means of several screws distributed on the periphery and the diaphragm is clamped therebetween. The difficulty of this fastening consists in that the screws do not uniformly clamp the diaphragm as it is not possible to tighten all screws to exactly the same compression distance. An uneven compression of the diaphragm may however lead to a leakage between the valve body and the diaphragm and to a reduction of the service life of the diaphragm itself. Furthermore, the several screws can easily be lost during mounting or demounting of the drive or could fall into the flow channel.
DE 101 53 362 A1 provides a fastening unit having a central union nut for connecting the drive to the valve body which permits a constant compression of the diaphragm. However, just in case of an overhead mounting, it is not always easy to assemble the partly heavy diaphragm valves after the valve body has usually been mounted into a drive train and possibly merely the diaphragm is to be replaced.
The invention provides a diaphragm valve in which the mounting of the drive and the replacement of the diaphragm are simplified and accelerated and a uniform and process reliable diaphragm clamping is ensured.